Information handling system antenna isolation with integrated cooling fan

ABSTRACT

A portable information handling system structure located between housing hinges along one side of the housing has first and second antenna disposed at opposing ends with a cooling fan between the first and second antenna and over the antenna structure to isolate the first and second antenna. In one embodiment, a parasitic element disposed between the first and second antenna and under the cooling fan has resonance tuned to isolate wireless signals of a frequency supported by the first and second antenna.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/220,653, filed Dec. 14, 2018, entitled “Information Handling SystemAntenna Isolation with Integrated Cooling Fan,” naming Ching Wei Chang,Suresh Ramasamy, Allen B. McKittrick, and Jeffery D. Kane as inventors,which application is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates in general to the field of informationhandling system wireless communication, and more particularly to aninformation handling system antenna isolation with an integrated coolingfan.

Description of the Related Art

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to users is information handling systems. Aninformation handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may also vary regarding what information is handled,how the information is handled, how much information is processed,stored, or communicated, and how quickly and efficiently the informationmay be processed, stored, or communicated. The variations in informationhandling systems allow for information handling systems to be general orconfigured for a specific user or specific use such as financialtransaction processing, airline reservations, enterprise data storage,or global communications. In addition, information handling systems mayinclude a variety of hardware and software components that may beconfigured to process, store, and communicate information and mayinclude one or more computer systems, data storage systems, andnetworking systems.

Portable information handling systems generally support mobileoperations with processing components, input/output (I/O) devices and apower source integrated in a portable housing so that an end user mayinteract with the system free from external cable interfaces. Forinstance, tablet information handling systems integrate processingcomponents and a battery in a planar housing covered by a touchscreendisplay that presents information as visual images and accepts touchesas inputs. Convertible information handling systems generally distributethe processing components, battery and display between two separaterotationally coupled housing portions with one housing portionintegrating the display and the other covered by a keyboard. A typicalconvertible information handling system rotates the housing portionsfrom a closed position that protects the display by rotating it next tothe keyboard to a clamshell position that holds the display verticallyabove the keyboard so an end user can type inputs at the keyboard whileviewing the display. Some convertible information handling systemsrotate the housing portions 360 degrees from the closed position toexpose the display for use as a tablet.

Generally portable information handling system length and widthdimensions are driven by the size of the display integrated in thehousing. Often, end user's select information handling systems for adisplay viewing area and then weigh desired processing capabilitiesagainst system height and weight. Generally, more powerful processingcomponents tend to have greater height and weight so that the processingcomponents have adequate power and thermal operating constraints. Assystem height decreases, thermal constraints in particular becomedifficult to manage as the internal housing cavity tends to have lessefficient cooling airflow. Some very thin systems maintain thermalconstraints by relying on passive thermal transfer instead of includinga cooling fan, however, active thermal management with a cooling fangenerally offers a substantial increase in thermal management of morepowerful processing components. Generally, information handling systemmanufacturers attempt to dispose processing components and activecooling resources in a portable housing in an efficient manner thatallows for low Z-height.

One way to reduce portable housing length and width dimensions is tointegrate the display in the housing with a narrow border along theperimeter of the display. Generally, to reduce the display border avariety of components typically included with the display housingportion are moved instead to the main housing portion. For instance,display housing portions often include a camera, microphone and wirelessantenna that are instead moved to the main housing portion. Moving suchcomponents to the main housing portion tends to crowd areas of the mainhousing portion where the components are most convenient, such as alongthe base of the display. Wireless antenna placement presents aparticular difficulty as the antenna radiation pattern faces increasedinterference and lower height in the main housing portion, which impedeswireless signal transfer. Further, to ensure adequate housing strengthin the face of torsional forces introduced by rotation around hinges,metallic housing material is typically used, which further impactswireless signal transfer. Although non-metallic windows may be includedin the housing, these areas create weakness, such as in the case of aphysical impact at the non-metallic window. In many cases, multipleantenna are included that communicate in shared frequency ranges, whichwill create isolation issues, especially within an all metal enclosure.

SUMMARY OF THE INVENTION

Therefore, a need has arisen for a system and method which isolatesradiofrequency elements located in close proximity in an informationhandling system portable housing.

In accordance with the present invention, a system and method areprovided which substantially reduce the disadvantages and problemsassociated with previous methods and systems for integrating antenna inan information handling system portable housing. An antenna structuredisposed along one side of a housing supports plural antenna separatedby a cooling fan disposed over the antenna structure to enhanceisolation. In one embodiment, a tunable parasitic element disposed underthe cooling fan exhaust further isolates the antenna.

More specifically, a portable information handling system processesinformation with processing components disposed in a housing havingrotationally coupled main and lid portions. A display integrated in thelid portion presents information as visual images with a narrow edge sothat antenna to support wireless communication are integrated in themain housing portion. An antenna support disposed along a rear side ofthe main housing portion supports first and second antenna at opposingends, such as LTE antenna to support wireless wide area network (WWAN)communication. Isolation between the antennas is provided by a groundedmetal housing of a cooling that exhausts between the antennas over theantenna support. In one embodiment, the cooling fan assembles in anopening formed in a motherboard and couples to a heat pipe thattransfers heat from a central processing unit (CPU) coupled to themotherboard. A tunable parasitic element disposed on the antenna supportbetween the antenna and under cooling fan adapts isolation to pluralfrequency bands based upon the isolation response of the cooling fan andheat pipe for each frequency band.

The present invention provides a number of important technicaladvantages. One example of an important technical advantage is that acooling fan assembles at an information handling system motherboardbetween wireless antenna to isolate the antenna, thus reducing mutualcoupling and improving radiofrequency efficiency. Grounded metalstructures of the cooling fan and heat transfer structure absorbsradiofrequency energy transferred between the antenna to allow placementof the antenna in close proximity within an information handling systemhousing with less impact upon desired radiofrequency transmissions.Leveraging metallic structure of a cooling fan to provide antennaisolation reduces the need to add other structures dedicated to antennaisolation. In one embodiment, a parasitic element is added to furtherreduce mutual coupling and tuned to adapt the parasitic response tochanging frequencies of the antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood, and its numerousobjects, features and advantages made apparent to those skilled in theart by referencing the accompanying drawings. The use of the samereference number throughout the several figures designates a like orsimilar element.

FIG. 1 depicts a top view of a portable information handling systemhaving plural antenna disposed in a main housing portion;

FIG. 2 depicts a bottom cutaway view of the portable informationhandling system having first and second antenna disposed proximate acooling fan exhaust;

FIG. 3 depicts a top view of an antenna structure having a cooling fanextending between antenna disposed on the antenna support;

FIG. 4 depicts a bottom view of an antenna structure having a coolingfan disposed on the antenna support;

FIG. 5 depicts a bottom exploded view of the antenna structureintegrated in a keyboard cover;

FIG. 6 depicts a top view of the antenna structure extending out fromthe keyboard and having the non-metallic cover removed;

FIG. 7 depicts a bottom view of the antenna structure extending out fromthe keyboard and having the non-metallic cover removed;

FIG. 8 depicts a side view of the antenna structure having thenon-metallic cover removed;

FIG. 9 depicts an upper perspective view of the antenna structure havingthe non-metallic cover removed;

FIG. 10 depicts a graph illustrating isolation performance of theantenna structure with the cooling fan over the antenna structure andwithdrawn from a position over the antenna structure;

FIG. 11 depicts a circuit block diagram of a radio module that adoptsparasitic element resonance based upon antenna frequency; and

FIG. 12 depicts a flow diagram of a process for adopting parasiticelement resonance based upon antenna frequency.

DETAILED DESCRIPTION

A portable information handling system assembles a cooling fan to extendover an antenna structure disposed along one side of a housing so that agrounded conductive surface of the cooling fan isolates the antenna fromeach other. For purposes of this disclosure, an information handlingsystem may include any instrumentality or aggregate of instrumentalitiesoperable to compute, classify, process, transmit, receive, retrieve,originate, switch, store, display, manifest, detect, record, reproduce,handle, or utilize any form of information, intelligence, or data forbusiness, scientific, control, or other purposes. For example, aninformation handling system may be a personal computer, a networkstorage device, or any other suitable device and may vary in size,shape, performance, functionality, and price. The information handlingsystem may include random access memory (RAM), one or more processingresources such as a central processing unit (CPU) or hardware orsoftware control logic, ROM, and/or other types of nonvolatile memory.Additional components of the information handling system may include oneor more disk drives, one or more network ports for communicating withexternal devices as well as various input and output (I/O) devices, suchas a keyboard, a mouse, and a video display. The information handlingsystem may also include one or more buses operable to transmitcommunications between the various hardware components.

Referring now to FIG. 1, a top view depicts a portable informationhandling system 10 having plural antenna 22 and 24 disposed in a mainhousing portion 12. In the example embodiment, main housing portion 12rotationally couples to a lid housing portion 14 with a pair of hinges16, such as dual axle hinges that provide 360 degrees of rotationalmovement of lid housing portion 14 relative to main housing portion 12.For instance, lid housing portion 14 rotates from a closed positionhaving a display 19 over top of a keyboard 18 to a clamshell position ofabout 90 degrees of rotation in which main housing portion 12 supportsdisplay 19 in a viewing position over keyboard 18 so that an end usercan type inputs while viewing display 19. As depicted, display 19 restson a support surface opposite keyboard 18 after about 180 degrees ofrotation, such as allows an end user to interact with a touchscreen ofdisplay 19 as a tablet. A full 360 degrees of rotation of lid housingportion 14 relative to main housing portion 12 disposes keyboard 18under display 19 to support mobile tablet interactions by an end user.In the example embodiment, main housing portion 12, lid housing portion14 and a cover that holds keyboard 18 in position have a metallicconstruction to provide structure support against torsional forcesintroduced during rotational movement. Further, display 19 integrates inlid housing portion 14 with a narrow edge construction that enhancesportability and provides a clean industrial design having imagespresented across the length and width of the lid housing portion.

Manufacture of information handling system 10 with a minimal boundarydisplay 19 and with a metallic housing presents difficulty for theeffective disposition of antenna in information handling system 10 tosupport wireless communication. In the example embodiment, an antennasupport 20 is coupled to main housing portion 12 between hinges 16 alongthe rear side of main housing portion 12 to provide wireless signalpathway in support of a pair of wireless wide area network (WWAN)antenna 22 and 24, such as to support communication with an LTE network.Placement of antenna 22 and 24 in close proximity can degrade antennaperformance due to mutual coupling of the antenna during transmissionsin channels, such as do to near field current effects. A parasiticelement 26 is disposed between antenna 22 and 24 to further aidisolation. For instance, antenna support 20 is a printed circuit boardhaving approximately 210 mm between hinges 16 with each antenna 22 and24 having a length of approximately 75 mm so a minimal space ofapproximately 55 mm exists to place parasitic element 26. Generally, aquarter wavelength of space is desired between antenna 22 and 24 toobtain sufficient isolation for reducing mutual coupling, however thatamount of space is difficult to find in main housing portion 12,especially where metallic material is desired for housing strength. Inthe example embodiment, wireless local area network antenna 27 and nearfield communication antenna 30 are also included and best operated witha clear wireless signal pathway. To obtain acceptable WWAN signalstrength, further isolation of antenna 22 and 24 is desirable.

Referring now to FIG. 2, bottom cutaway view depicts portableinformation handling system 10 having first and second antenna 22 and 24disposed proximate a cooling fan 34 exhaust. Information handling system10 processes information with a central processing unit (CPU) 28 thatexecutes instructions and a random access memory (RAM) that stores theinformation and instructions. To remove excess thermal energy generatedby CPU 28, a heat sink and heat pipe 32 thermally couple to CPU 28 totransfer thermal energy towards a cooling fan 34. Cooling fan 34generates a cooling airflow past heat pipe 32 to draw thermal energy outof main housing portion 12.

In the example embodiment, cooling fan 34 has a metallic or otherconductive housing material and is placed to exhaust over top ofparasitic element 26. In the example position depicted, cooling fan 34is placed between antenna 22 and 24 to aid in isolation of each ofantenna 22 and 24. For example, radio 50 grounded to a motherboard inmain housing portion 12 communicates wireless signals to antenna 22 and24 through a coaxial cable interface. Antenna support 20 grounds usinggaskets with metal material extending from a keyboard cover describedbelow. Cooling fan 34 couples to and grounds to the motherboard thatsupports radio 50, as does heat pipe 32. With the grounded metalstructure of cooling fan 34 disposed between antenna 22 and 24,isolation of antenna 22 and 24 is enhanced. Further, parasitic element26 provides isolation by, in effect, forcing surface currents related tomutual coupling to travel along the ground plane, essentially creating alonger path for current to follow and making up for the “shortfall” inspacing between antenna 22 and 24.

Referring now to FIG. 3, a top view depicts an antenna support 20 havinga cooling fan 34 extending between antenna 22 and 24 disposed on theantenna support 20. Antenna support 20 has a side wall extendingdownward that defines an exhaust through which cooling fan 34 expelsheated airflow. For the upper view of FIG. 3, antenna support 20 isplaced over cooling fan 34. Referring now to FIG. 4, a bottom viewdepicts antenna support 20 having cooling fan 34 disposed on the antennasupport. Antenna 22 and 24 are formed on perpendicular sides of antennasupport 20 with cooling fan 34 abutted against the back side of antennasupport 20. Placement of cooling fan 34 in between antenna 22 and 24creates a metal structure inserted between the antenna that acts as anisolator, shield and grounding mechanism that aid antenna performance.The intersection 36 of cooling fan 34 and antenna support 20 definesantenna isolation between antenna 22 and 24 that are formed on opposingends of antenna support 20.

Referring now to FIG. 5, a bottom exploded view depicts antenna support20 integrated in a keyboard cover 44. In the example embodiment, coolingfan 34 is sized to fit in an opening formed in motherboard 38 thataligns cooling fan 34 between antenna 22 and 24. The opening inmotherboard 38 allows freedom along the Z-axis or height of informationhandling system 10 to adjust placement of cooling fan 34 in a mannerrelative to antenna 22 and 24 that optimizes radiofrequency isolation,thus improving antenna performance. Heat pipe 32 is formed as necessaryto fit over CPU 28 and communicate thermal energy from CPU 28 to theexhaust of cooling fan 34. In the example embodiment, antenna support 20defines antenna 22 and 24 on a flexible printed circuit board foldedinto perpendicular sections and held in position by a plastic moldedsupport 42 and interfaced through a cable connection 40. Support 42couples to a radiofrequency window 46 integrated in a keyboard cover 44,such as with snaps or other coupling mechanisms. For example,radiofrequency window 46 has a hardened thermoplastic material that alsoforms an exhaust vent 48 for exhaust of cooling fan 34. Keyboard cover44 is a metallic material, such as aluminum, that provides increasedstructural strength to help resist torsional forces introduced at a lowZ-height housing during rotational movement. Metallic members 49 extenddownward from keyboard cover 44 proximate window 46 to help furtherisolate antenna 22 and 24. For example, antenna support 20 is groundedto members 49 with gaskets so that members 49, cover 44, cooling fan 34,heat pipe 32 and motherboard 38 all share a common ground. In addition,members 49 aid in capture and retention of antenna support 20.

Referring now to FIG. 6, top view depicts the antenna support 20extending out from the keyboard and having the radiofrequency window 46removed. Keyboard 18 extends through key openings formed in cover 44 toaccept key inputs from an end user. Antenna support 20 extends outwardfrom cover 44 to provide a clear radiofrequency pathway for transmissionof wireless signals. As explained above, cooling fan 34 fits underparasitic element 26 midway between antenna 22 and 24. Referring now toFIG. 7, a bottom view depicts antenna support 20 extending out from thekeyboard 18 and having the radiofrequency window 46 removed. From thebottom view, placement of cooling fan 34 over parasitic element 26 andbetween antenna 22 and 24 is illustrated. Referring now to FIG. 8 a sideview depicts antenna support 20 having the radiofrequency window 46removed. Cooling fan exhaust 48 formed in the plastic molded support 42of antenna support 20 provides openings through which cooling fan 34exhausts heated air.

Referring now to FIG. 9 an upper perspective view depicts the antennasupport 20 having the radiofrequency window 46 removed. In the exampleembodiment, antenna 22 supports auxiliary LTE communications and antenna24 supports main LTE communications. Each of antenna 22 and 24 areprinted circuits defined in a flexible printed circuit board and foldedover a non-conductive plastic molded support base 42 to extend outwardfrom keyboard 18 and cover 44. Parasitic element 26 is disposed betweenantenna 22 and antenna 24 and tuned to reduce mutual coupling, such ascan be caused by surface currents extending between antenna 22 andantenna 24. As illustrated by FIG. 9, parasitic element 26 may includeconductive elements that extend downward between cooling fan 34 exhaust48 openings. In various embodiments, antenna and parasitic elementprinted circuits may have various forms as desired to transmit desiredwireless signals, such as WLAN signals, and with various antennaconfigurations, such as MIMO antenna configurations. Antenna tuning willdepend upon the desired wireless transmission signal frequencies, thespace between hinges of the housing that is available for the antennastructure, and the relationship between system ground and the antennawhere ground may include cooling fan 34 and heat pipe 32.

Referring now to FIG. 10 a graph illustrates isolation performance ofthe antenna support 20 with cooling fan 34 over antenna support 20 andwithdrawn from a position over the antenna support. The example graphincludes S-parameters in dB for antenna interference with cooling fan 34pushed into position between antenna 22 and 24, and for cooling fan 34pushed backwards away from antenna 22 and 24. Although antennaperformance varies along the radiofrequency spectrum and targets desiredtransmission bands, generally an improvement of 20 dB in antennaefficiency is provided by improved isolation resulting from placement ofcooling fan 34 between antenna 22 and 24. The improved performance isgenerally provided in a restricted space by disruption of mutualcoupling with the shared ground structures, however, as frequency shiftsbetween different bands, resonance of the mutual coupling shifts so thattuning of the ground response can further adjust antenna performance.

Referring now to FIG. 11, a circuit block diagram depicts a radio module50 that adopts parasitic element 26 resonance based upon antennafrequency. In the example embodiment, radio module 50 is an integratedcircuit having GPIO and/MIPI interfaces to control antenna and parasiticelement resonance. Radio module 50 communicates wireless signals toantenna 22 and 24 through RF ports 52 and 54 and an impedance switch andtuner 56 and 58 disposed between each antenna 22 and 24. In the exampleembodiment, radio module 50 tunes antenna 22 and antenna 24 to supportfour different LTE frequency bands: B12 (698-746 MHz); B29/28/13/14(717-798 MHz); B26/19/18/5/6/20 (814-894 MHz); and B8 (880-960 MHz). Forexample, impedance switch and tuner 56 and 58 selects LC circuit valuesto match antenna 22 and 24 impedance to the frequency of radio module50. Radiofrequency tuning may also depend upon detection of bodiesproximate to antenna 22 and antenna 24, such as may introduce near fieldeffects that interfere with antenna impedance tuning. For example, aHall sensor 66 is monitored by sensor logic 68 to trigger a sensor hub64, such as when a tablet mode rotates the housing portions in proximityto each other. Radio module 50 may select impedance tuning settings forantenna 22 and 24 based upon a trigger from such a proximity detection.

As an example, of impedance tuning based upon inputs by a Hall sensor66, radio module 50 stores antenna impedance tuning states for each ofplural housing configurations and applies the stored antenna impedancetuning states based upon Hall sensor output. For instance, in aclamshell mode Hall sensor 66 detects the rotational orientation of lidhousing portion 14 rotated 90 degrees relative to main housing portion12. In response to detection of clamshell mode, radio module 50 looks upimpedance values for the selected LTE band at a clamshell rotationalorientation and applies the impedance values to adjust the impedance ofantenna 22 and 24 and parasitic element 26. The impedance values reflectan expected impact on radiofrequency characteristics for the relativeposition of lid housing portion 14 to antenna support 20, such as nearfield effects created by the metal material of lid housing portion 14.In various embodiments, stored impedance values to apply to antenna 22and 24 and to parasitic element 26 may be kept for a variety oforientations of lid housing portion 14 relative to main housing portion12 as desired based upon experiment antenna performance. Furtheradjustment of antenna impedance may be performed by measuring capacitiveeffects associated with the proximity of lid housing portion 14 toantenna support 20, such as by monitoring capacitance to detect objectproximity, such as to maintain SAR constraints as set forth in U.S.patent application Ser. No. 16/221,046, filed Dec. 14, 2018, by ChingWei Chang, entitled “Information Handling System Radio Transmit PowerManagement” and filed concurrently with the present application, whichis incorporated herein as if fully set forth.

In addition to tuning antenna 22 and 24, a GPIO interface 62 of radiomodule 50 interfaces through an SP4T switch 60 or similar selectionstructure to tune parasitic element 26. For example, SP4T switch 60 hasa setting for each of the four LTE frequency band groups describedabove. The isolation performance of parasitic element 26 varies basedupon the ground structure interfaced with it. For instance, the size ofthe conductive housing of cooling fan 34 and the length of heat pipe 32will each impact the isolation of mutual coupling between antenna 22 and24 provided by parasitic element 26. Thus, in various embodiments, logicin radio module 50 considers the frequency at which antenna 22 and 24communicate, the size and length of ground structures interfaced withantenna structure 20, and the detection of proximate object when settingresonance of parasitic element 26.

Referring now to FIG. 12, a flow diagram depicts a process for adoptingparasitic element resonance based upon antenna frequency. At step 70, adefault state 76 is initially set through switch 78 for a defaultantenna tuning frequency. At step 72 a determination is made of whetherthe LTE band has changed for the wireless communication to a differentstate, such as one of the groups of frequency bands describe above. Ifnot, the process returns to step 70 to continue monitoring the radio'scommunication band. If a change in communication band is detected atstep 72, the process continues to step 74 to command switch 78 to tuneparasitic element 26 to adjust mutual coupling isolation based upon thetuning of antenna 22 and antenna 24. In alternative embodiments,isolation tuning may involve multiple interactions across differentfrequency bands. For instance, the four states described in the aboveexample cover 700 MHz to approximately 960 MHz, the low band of LTE;however, in alternative embodiments, a wider band of coverage may beprovided with additional switch configurations as needed to supportdesired wireless protocols.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions and alterations can bemade hereto without departing from the spirit and scope of the inventionas defined by the appended claims.

What is claimed is:
 1. A method for communicating wireless signals at aportable information handling system, the method comprising: coupling afirst antenna and a second antenna along one side of the portableinformation handling system housing; coupling a cooling fan to exhaustair at the one side of the portable information handling system housingbetween the first antenna and the second antenna; communicating wirelesssignals from the first antenna and the second antenna; and isolatingwireless signal interference between the first antenna and the secondantenna with a grounded metallic material of the cooling fan disposedbetween the first antenna and the second antenna.
 2. The method of claim1 wherein the coupling the first antenna and the second antenna furthercomprises: coupling the first antenna and the second antenna to anantenna support separate from a motherboard of the portable informationhandling system; and extending the cooling fan from the motherboardacross the antenna support between the first antenna and the secondantenna.
 3. The method of claim 2 wherein the coupling a cooling fanfurther comprises: forming an opening in the motherboard extending fromthe one side of the information handling system towards an opposing sideof the information handling system, the opening configured to fit thecooling fan; coupling the cooling fan in the opening.
 4. The method ofclaim 2 further comprising: disposing a parasitic element on the antennasupport between the first antenna and the second antenna and below thecooling fan; and tuning the parasitic element to isolate the firstantenna and the second antenna.
 5. The method of claim 2 furthercomprising: coupling a heat pipe at a first end to the cooling fan andat a second end to a processor coupled to the motherboard; and tuningthe parasitic element to isolate the first antenna and the secondantenna based in part upon a length of the heat pipe.
 6. The method ofclaim 2 further comprising: coupling a metal keyboard cover over thecooling fan, the metal keyboard cover having a nonmetallic portion; andaligning the nonmetallic portion over the first antenna and the secondantenna.
 7. The method of claim 6 further comprising extending a firstmetallic member and a second metallic member downward from the keyboardcover towards the motherboard, the first metallic member aligned withthe first antenna, the second metallic member aligned with the secondantenna.